Effect of single- and multiple-dose 0.5% timolol maleate on intraocular pressure and pupil size in female horses.

This research study investigates the effects of single and multiple doses of 0.5% timolol maleate, a medication, on intraocular pressure and pupil size in female horses. It finds that administering this medication both once and multiple times significantly decreases intraocular pressure and pupil size in these horses.

Study Objective and Procedure

• The objective of this research was to examine the effects of the application of 0.5% timolol maleate, a drug usually used to treat glaucoma and high eye pressure, on the intraocular pressure (pressure inside the eye) and pupil size in female horses. The study focused specifically on the differences between the effects of single doses and multiple doses applied twice daily.
• To determine these effects, the researchers took a sample of nine female horses with normotensive eyes. They then measured the horses’ IOP (intraocular pressure), horizontal pupil size, and vertical pupil size multiple times on a single day from 8 AM to 8 PM, at specific hours (0, 0.5, 1, 2, 4, 6, 8, 10, and 12 hours).
• After the initial measurements, they applied a single dose of 0.5% timolol maleate to both eyes of each horse, just after the first measurement at 8 AM. They then conducted another experiment where they applied the 0.5% timolol maleate twice daily (at 8 AM and 4 PM) over a 5-day period, measuring the IOP and pupil size of each horse on each day at the same time.

Study Results

• The results of the study showed a significant decrease in IOP from an average of 24.9 mmHg before application to 20.7 mmHg 8 hours after a single application of the medication. This translates to a 17% decrease.
• In addition, there was a significant reduction in horizontal pupil size by 11%, which was observed 6 hours after applying the single dose.
• In the multiple-dose experiment, a significant decrease in IOP was observed on the 4th and 5th days as compared to the measurements obtained prior to the application of the medication.
• Horizontal and vertical pupil size also significantly decreased throughout the 5-day study compared to pre-treatment measurements.

Study Conclusion

• The study concludes that the use of 0.5% timolol maleate significantly reduces both IOP and pupil size in normotensive (normal blood pressure) female horses, irrespective of whether it is applied once or multiple times a day.

By demonstrating these effects, the study suggests that 0.5% timolol maleate could potentially be a useful treatment for conditions related to high intraocular pressure in horses, like glaucoma.